1. Field of the Invention
This invention relates to liquid smoke-containing food casings, and more particularly, to cellulose casings which have been treated so as to inhibit the formation of black spots on the liquid smoke-containing cellulose casings.
2. Description of the Prior Art
Surface appearance, odor and flavor are important factors in the commercial and consumer acceptance of processed meat products, and a common feature of most varieties of such products involves the use of "smoking" for imparting characteristic flavor, odor and color thereto. The "smoking" of food products has been generally accomplished by subjecting the food product to actual contact with smoke in a gaseous or cloud-like form. Such "smoking" processes, however, have not been considered completely satisfactory for a variety of reasons, including the inefficiencies and lack of uniformity of the "smoking" operation. Because of the shortcomings experienced, many meat packers now employ various types of aqueous solutions of wood-derived smoke constituents, commonly called "liquid smoke solutions", in the processing of many types of meat and other food products.
The application of "liquid smoke solutions" to meat products is generally carried out in a variety of ways, including spraying or dipping an encased food product during the processing thereof, but this is not completely satisfactory because of inability to uniformly treat the encased product. Another method is to incorporate the liquid smoke solution in the recipe itself, but this does not always provide the desired surface appearance because of dilution of smoke ingredients. Also, incorporation of liquid smoke in the recipe reduces the stability of the meat emulsion, and will adversely affect taste if high concentrations are used. Spray or dip application of liquid smoke to encased food products also causes unwanted pollution and equipment corrosion problems for the food processor. In addition, encased foodstuffs treated by application of the liquid smoke during commercial processing have been found to yield sausages which are lacking in smoke color uniformity between different sausages from the same processed group. Even more undesirable is the lack of color uniformity which often appears on the surface of the same sausage, such as light and dark streaks or blotches, and even uncolored spots, particularly at the sausage ends.
It has been found that casings affording special treatment or structural characteristics to the food product can be more uniformly and economically supplied by the casing manufacturer. Accordingly, it would be desirable for the casing manufacturer to provide a liquid smoke-impregnated casing which could be used by the food processor to impart smoke flavor, odor and color to the food product after stuffing in the casing and during the elevated temperature processing of the encased product.
Liquid smoke often is a solution of natural wood smoke constituents prepared by burning a wood, for example, hickory or maple, and capturing the natural smoke constituents in a liquid medium such as water. Alternatively, the liquid smoke to be used may be derived from the destructive distillation of wood, that is, the breakdown or cracking of the wood fibers into various compounds which are distilled out of the wood char residue. Aqueous liquid smokes are generally very acidic, usually having a pH of 2.5 or less and a titratable acidity of at least 3%.
Reference to the term "smoke color, odor and flavor constituents", as used throughout this specification with respect to liquid smoke compositions and the liquid smoke-impregnated casing article of this invention, is intended to refer to, and should be understood as referring to, the smoke coloring and flavoring and odor constituents derived from liquid smoke solutions in their commercially available form.
The liquid smoke used to prepare the article of this invention is derived from natural wood smoke constituents. The source liquid smoke is generally produced by the limited burning of hardwoods and the absorption of the smoke so generated, into an aqueous solution under controlled conditions. The limited burning keeps some of the undesirable hydrocarbon compounds or tars in an insoluble form, thereby allowing removal of these constituents from the final liquid smoke. Thus, by this procedure, the wood constituents previously considered desirable by the manufacturer of the liquid smoke are absorbed into the solution in a balanced proportion and the undesirable constituents may be removed. The resultant liquid smoke solution still contains a significant concentration of tars, because the manufacturers and users of the liquid smoke consider the dark colored tars to be necessary from the standpoint of imparting smoke color, odor and flavor to foodstuffs.
Smoke treatment is quite expensive, and it has been assumed in the meat packing industry that to achieve the darker smoke color characteristic on the surface of a meat product, the encased meat product must be subjected to a more extensive treatment with smoke. This has typically been accomplished by increasing the treatment temperature, the contacting time, or the concentration of the liquid smoke, all of which result in increasing processing cost.
Food casings that are suitable for use in the present invention are tubular casings, and preferably tubular cellulosic casings, that are prepared by any one of the methods well known in the art. Such casings are generally flexible, thin-walled seamless tubing formed of regenerated cellulose, cellulose ethers such as hydroxyethyl cellulose, and the like, in a variety of diameters. Also suitable are tubular cellulosic casings having a fibrous reinforcing web embedded in the wall thereof, which are commonly called "fibrous food casings", as well as cellulosic casings without the fibrous reinforcement, herein referred to as "non-fibrous" cellulosic casings.
Casings conventionally known as "dry stock casings" may be used in the practice of this invention. Such casings generally have a water content within the range of from about 5 to about 14 weight percent of water if non-fibrous casing, or within the range of from about 3 to about 8 weight percent of water if fibrous casing, based on the total weight of casing including water.
Casings conventionally known as "gel stock casings" are casings which have higher moisture contents since they have not been previously dried, and such casings may also be used in the practice of this invention. Gel stock casings include fibrous or non-fibrous casings.
In the preparation and use of cellulosic food casings, the moisture content of the casings is of considerable importance. By way of non-limiting illustration, the casings may be shirred, i.e., compressed into a tightly compacted and pleated form, for use on a stuffing machine which deshirrs the shirred casing "stick" as the machine stuffs the deshirred casing. To facilitate shirring operations on fibrous cellulosic food casings without damaging them, it is generally necessary that they be of a water content in the range of from about 11% to about 26% by weight of total casing. To permit shirred casing to be stuffed without breaking the casing during the stuffing operation, shirred fibrous casings having an average moisture content of between about 17% to about 35% are required. This lower limit of moisture content is important during stuffing, because excessive breakage of the casing has been found to occur at lower moisture contents.
Here it is of importance to note that the term "moisture content" as used throughout this specification and in the appended claims with reference to the liquid smoke smoke-impregnated cellulosic casing articles of the invention, is intended to refer to and should, unless otherwise specified, be understood as referring to: the weight percent of water or moisture in the casing based on the total weight of the casing.
Even if large size casings are to be used in the flattened form for stuffing without conversion to the shirred stick form, such large size casings are quite stiff in the dry stock form, and are softened for stuffing operation by soaking in water, usually for about an hour, typically resulting in full moisture saturation of the casing to about 60% by weight of the total casing. Because of this full saturation soaking just prior to use in stuffing operations, the furnishing of such flat stock casings with any predetermined controllably added moisture content for stuffing operations has not been necessary or even advantageous.
The recent wider use of automatic high speed high pressure stuffing equipment for products employing large size tubular food casings, and the consequent increased demand for such casings in shirred form as compared to the short, flattened lengths heretofore used, has brought focus to bear on and has emphasized the problems of moisturizing such casings by soaking just prior to use. Moreover, the need for greater control of all aspects of the manufacture and use of large size food casings has been and is increasing. For example, the uniformity of dimensions of stuffed food casings and food products processed therein has become an increasingly important commercial requirement, and casing moisture content has been found to be a factor in control of uniformity, as well as in meeting the continuing need to readily, and economically stuff the casings without damage or breakage thereof and, more importantly, to permit the stuffing of a given casing to its manufacturer's recommended fully stuffed size with consistent accuracy and reproducibility of results (size uniformity).
However, it has been found that liquid smoke-treated shirred cellulosic nonfibrous food casings, i.e., those without fiber reinforcement, having a relatively high moisture content develop dark discolorations upon storage. The dark discolorations are aptly termed "black spots". These black spots in time, for example, after about three months, represent a weakened area in the food casings which is susceptible to pinholing under stress and breakage during stuffing. It has been found that the areas of the black spots are contaminated with higher levels of iron compared to the clear areas of the casings. In the black spot areas of the casings, film deterioration may be experienced in a variety of stages from no visible damage, to blister separations, to actual holes. In addition, it has been observed that the black spots on the casings occasionally transfer to the food emulsion, thereby affecting the aesthetic character of the food product.
Further, there have been found to be two main types of black spots, intense and diffuse. Intense black spots are darker and more concentrated, and are often associated with a particle of foreign material which appears to seed the discoloration. The diffuse type of black spot has no intense color center, but appears as a general discoloration of the casing in a particular area thereof. Analysis of the intense black spot areas indicate high iron concentrations in the immediate area of the spot. In comparison, analysis of diffuse discolored areas show very slight increased iron concentration.
It has been found in water burst and stuffing performance tests that the casing degrades in the area of the black spot after about three months of storage so as to cause the potential for breakage, either during casing storage or subsequently during stuffing. Also, while the black spots are visible in high moisture content fibrous casings, breakage is not as prevalent as in non-fibrous casing due to the inherent strength provided by the fibrous reinforcing web.
Various attempts have been made to prevent black spot formation upon liquid smoke treated food casings. These attempts have included better housekeeping, using cleaning devices for the various machinery process steps such as during the casing shirring step, and cleaning the glycerine addition via submicron filtration. These attempts to avoid or minimize iron contamination have provided improvements in reducing black spot formation on liquid smoke treated casings during storage, but they have not provided completely satisfactory results, such as totally eliminating their formation. Thus, there is a continuing need for a process and a composition to prevent the formation of black spots on liquid smoke treated food casings and to overcome the above-noted disadvantages.